A 1480 kg car is coasting along a level road at 28.3 m/s. A constultant braking force is applied such that the car is stopped in a distance of 68.9m. What is the magnitude of the braking force? Answer in units of N.
2006-10-27 20:32:36 · 7 answers · asked by invu 1 in Science & Mathematics ➔ Physics
Use the basic motion laws to find acceleration:
Given data is
m=1480.7 kg
vinitial=28.3m/s
vfinal=0
d=68.9m
vf^2=vi^2+2ad
(vf^2-vi^2)/2d=a=(0)(0)-(28.3m/s)(28.3m/s)/
2(68.9m)=
-800.89/137.8m=-5.81m/s^2
There now that you have the acceleration you must remember Newton's First Law of motion
F=ma
as such F=(1480.7kg)(-5.81m/s^2)
=8602.867N(sig digits)
=8.60*10^3N
or use Kinetic energy,work,potential energy, conservation of energy laws to solve same thing
KE=1/2m(vf^2-vi^2)
Note:in this equation since we know final velocity is o it can be excluded from the equation giving
KE=1/2mv^2=1/2(1480.7)(800.89)
=592938.9J
Kintetic energy=Work=Potential energy=Mechanical Energy in such a system
As such KE=Work
Work or W=Fd
since KE=W=Fd
F=KE/d=592938.9J/68.9m=8606N(sig digits)=8.61*10^3
see both methods give the same answer, kind of cool
2006-10-27 20:37:07 · answer #1 · answered by Zidane 3 · 0⤊ 0⤋
The simplest way to solve this problem is to use the conservation of energy principle.
Kinetic energy=Work energy
1/2mv^2=f*s
m is the mass of the car =1480kg
v=its velocity=28.3m/s
f=the braking force
s=the displacement in meters=68.9m
substitute known values:
1/2*1480*28.3^2=f*68.9
592658.6=f*68.9
f=592658.6/68.9
=8601.7 N
2006-10-27 21:06:24 · answer #2 · answered by tul b 3 · 0⤊ 0⤋
The kinetic energy lost = ½ m v v.
This is equal to force x displacement =F x s.
F* s = ½ m v v.
F = ½ m v v / s.
F =( ½ ) 1480.7 x 28.3 x 28.3 / 68.9 = 8606 N.
2006-10-27 21:40:22 · answer #3 · answered by Pearlsawme 7 · 0⤊ 0⤋
v^2 = 2as
so a = v^2/2s = 28.3^2 / 2 / 68.9 = 5.812 m/s^2
F = ma = 1480.7 * 5.812 = 8605.79 N
2006-10-27 20:48:45 · answer #4 · answered by The Potter Boy 3 · 0⤊ 0⤋
v^2-u^2 =2as
v=0
u=28.3
s=68.9
therefore
a=0-(28.3)^2/2(68.9)=5.81m/s^2
F=ma =1480.7(5.81)=8605.79 N
2006-10-27 21:27:53 · answer #5 · answered by Anonymous · 0⤊ 0⤋
Work is force times distance.
Work is the kinetic energy that was removed from the car, and you have the distance.
2006-10-27 20:35:18 · answer #6 · answered by arbiter007 6 · 0⤊ 0⤋
f= ma.
v^2=u^2 - 2as
from the 2nd equation find a. (v=0)
substitute in f=ma and find f.
use a calculator...
the final answer will be in newtons if u use the given units.
2006-10-27 20:42:00 · answer #7 · answered by muradak_1 2 · 0⤊ 0⤋